Plasma poisoning to enable selective deposition

ABSTRACT

Atomic layer deposition in selected zones of a workpiece surface is accomplished by transforming the surfaces outside the selected zones to a hydrophobic state while the materials in the selected zones remain hydrophilic.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 15/075,046, filed on Mar. 18, 2016, the entirecontents of which is hereby incorporated by reference.

BACKGROUND Technical Field

The disclosure concerns a method of forming layered structures by atomiclayer deposition of materials, in accordance with a predeterminedpattern of different materials in an integrated circuit.

Background Discussion

In some fabrication processes for forming integrated circuits, it isdesirable to deposit thin films by atomic layer deposition (ALD) inaccordance with a predetermined pattern. The pattern defines selectiveareas on a workpiece surface for deposition by an ALD process, while ALDis prevented in the other areas. Such a process is referred to herein asselective area atomic layer deposition. The problem is how to accuratelygovern the boundaries of the selective areas.

SUMMARY

A first method of performing atomic layer deposition in selected zonesof a workpiece comprises: (a) providing a surface in each of theselected zones of a first material of a first type that is initiallyhydrophilic and that becomes hydrophobic upon treatment with afluoro-carbon plasma or fluoro-carbon ion beam; (b) providing a surfaceof a second material in other zones of the workpiece that remainshydrophilic upon treatment with a fluoro-carbon plasma or fluoro-carbonion beam; (c) performing a plasma treatment on the workpiece using aplasma derived from a fluoro-carbon species; and (d) performing anatomic layer deposition process on the workpiece, and growing an atomiclayer of a growth material on surfaces of the selected zones whilegenerally avoiding growth of an atomic layer of the growth material inthe other zones.

In one embodiment, the first material comprises any material thatbecomes hydrophilic upon treatment with a fluoro-carbon plasma orfluoro-carbon ion beam, such as (but not limited to) for example one ofW, Co, SiN, T-oxide, TEOS or Si. In one embodiment, the second materialcomprises any material that remains hydrophilic upon treatment with afluoro-carbon plasma or fluoro-carbon ion beam, such as (but not limitedto) one of Cu or TiN. In one embodiment, the growth material comprises ametal or an oxide of a metal.

In one embodiment, the method is repeated until a desired thickness ofthe growth material is reached.

In one embodiment, the method further comprises removing growth materialdefects in the other zones.

A second method of performing atomic layer deposition in selected zonesof a workpiece comprises: (a) depositing a first photolithographic maskon the workpiece comprising first openings corresponding to portions ofthe selected zones; (b) treating the workpiece by exposure to speciesderived from a fluoro-carbon plasma; (c) removing the firstphotolithographic mask; (d) depositing a second photolithographic maskon the workpiece comprising second openings corresponding to remainingportions of the selected zones; (e) treating the workpiece by exposureto species derived from a fluoro-carbon plasma; (f) removing the secondphotolithographic mask; and (g) performing an atomic layer depositionprocess.

In one embodiment, the method further comprises removing growth materialfrom areas outside of the selected zones.

In one embodiment, the treating the workpiece comprises forming afluoro-carbon plasma and exposing the workpiece to the plasma. In oneembodiment, the treating the workpiece comprises forming an ion beamfrom a fluoro-carbon plasma and directing the ion beam to the workpiece.

In one embodiment, the atomic layer deposition process produces a growthmaterial. The growth material may be any material that can be formed byatomic layer deposition such as (but not limited to) metal, a non-metalor a metal oxide.

A third method of performing atomic layer deposition in selected zonesof a workpiece comprises: (a) depositing a first photolithographic maskon the workpiece comprising first openings corresponding to portions ofthe selected zones; (b) treating the workpiece by exposure to speciesderived from a fluoro-carbon plasma; (c) removing the firstphotolithographic mask; (d) performing a first atomic layer depositionprocess on the workpiece; (e) depositing a second photolithographic maskon the workpiece comprising second openings corresponding to remainingportions of the selected zones; (f) treating the workpiece by exposureto species derived from a fluoro-carbon plasma; (g) removing the secondphotolithographic mask; and (h) performing a second atomic layerdeposition process.

In one embodiment, the first and second atomic layer depositionprocesses deposit different growth materials on the workpiece.

In one embodiment, the treating the workpiece comprises forming afluoro-carbon plasma and exposing the workpiece to the plasma. In oneembodiment, the treating the workpiece by exposure to species derivedfrom a fluoro-carbon plasma comprises forming an ion beam from afluoro-carbon plasma and directing the ion beam to the workpiece.

In one embodiment, the first and second atomic layer deposition processproduce on the workpiece different respective growth materials.

A first method of performing atomic layer deposition in selected zonesof a workpiece having 3-dimensional structures on a surface thereofcomprising vertical walls separated by trenches, comprises: (a)providing a directional plasma source emitting ions along an ionpropagation direction toward the workpiece; (b) orienting the ionpropagation direction relative to the vertical walls to enable thevertical walls to mask the selected zones from the ions emitted by thedirectional plasma source; and (c) performing an atomic layer depositionprocess on the workpiece.

In one embodiment, the directional plasma source emits ions in two beamstilted relative to the vertical walls through opposing angles and thetwo beams strike opposing ones of the vertical walls.

In one embodiment, the directional plasma source emits a beam tiltedrelative to the vertical walls and the beams strikes one of the verticalwalls.

In one embodiment, the directional plasma source emits ions in one beamparallel to the vertical walls.

BRIEF DESCRIPION OF THE DRAWINGS

So that the manner in which the exemplary embodiments of the presentinvention are attained can be understood in detail, a more particulardescription of the invention, briefly summarized above, may be had byreference to the embodiments thereof which are illustrated in theappended drawings. It is to be appreciated that certain well knownprocesses are not discussed herein in order to not obscure theinvention.

FIGS. 1A, 1B, 1C, 1D, 1E, 1F, 1G and 1H depict successive operations ofa process performed on a workpiece in accordance with a firstembodiment.

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G and 2H depict successive operations ofa process performed on a workpiece in accordance with a secondembodiment.

FIGS. 3A, 3B, 3C, 3D, 3E, 3F, 3G and 3H depict successive operations ofa process performed on a workpiece, in accordance with a thirdembodiment

FIGS. 4A and 4B depict successive operations of a process performed on aworkpiece in accordance with a fourth embodiment.

FIGS. 5A and 5B depict successive operations of a process performed on aworkpiece in accordance with a fifth embodiment.

FIGS. 6A and 6B depict successive operations of a process performed on aworkpiece in accordance with a fifth embodiment.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation. It is to be noted, however, that the appendeddrawings illustrate only exemplary embodiments of this invention and aretherefore not to be considered limiting of its scope, for the inventionmay admit to other equally effective embodiments.

DETAILED DESCRIPTION

Selective ALD formation of a deposited film employs plasma poisoning ofthe workpiece surface in accordance with a desired pattern. Afluoro-carbon plasma treats selected areas of the workpiece surface totransform those selected areas from a hydrophilic state to a hydrophobicstate. Certain ALD processes are enabled on hydrophilic surfaces anddisabled on hydrophobic surfaces. In essence, the fluoro-carbon plasmatreatment altered (poisoned) the surface to prevent ALD formation ofdeposited films.

The pattern may be established in various ways. One way (Method I) is toprovide a first material only in selective surface areas, the firstmaterial being one that becomes hydrophobic upon exposure to afluoro-carbon. The remaining areas consist of a second material thatremains hydrophilic. Another way (Method II) is to provide a materialthat is hydrophilic unless treated by a fluoro-carbon plasma, in whichcase it becomes hydrophobic. In this latter case, the desired pattern isrealized by masking the selected surface areas during the plasmatreatment. This masking may employ photoresist, for example. Yet anotherway (Method C) is to employ a directional plasma beam so as to exploit3-dimensional features on the surface to shadow the plasma beam fromselected portions of the surface.

FIGS. 1A though 1H depict a first embodiment that employs Method I. FIG.1A depicts a workpiece surface 100 having two or more zones 105-1(Material A), 105-2 (Material B), 105-3 (Material C) of differentcharacteristics. In FIG. 1B, the workpiece is subjected to a plasmatreatment. The plasma treatment may be carried out by ion implantationof a fluoro-carbon species, or by exposure to an ion beam from afluoro-carbon plasma (e.g., CF4). The plasma treatment forms a plasmatreated surface layer 170. In the illustrated example, Materials A and Cbecome hydrophobic upon plasma treatment by a fluoro-carbon plasma,while material B remains hydrophilic, as indicated symbolically in FIG.1C. Next, as depicted in FIG. 1D, an ALD process is performed. Theresult is depicted in FIG. 1E, in which ALD deposition occurs only onMaterial B in zone 105-2. This is because Material B is hydrophilic,while Materials A and C are hydrophobic. FIG. 1F depicts an example inwhich the operation of FIG. 1D left small ALD deposits 115 in unselectedareas. In this case, an ALD clean-up step depicted in FIG. 1G isperformed, which removes the unwanted ALD deposits, and the thickness ofthe ALD deposited film in zone 105-2 is slightly reduced, as depicted inFIG. 1H.

Materials A and C, which become hydrophobic upon exposure to afluoro-carbon plasma, can be selected from a wide range of materials,such as (but not limited to) W, Co, SiN, T-oxide, TEOS, a nitride, ametal, a metal oxide, a semiconductor or Si. Material B, which remainshydrophilic after exposure to a fluoro-carbon plasma, may be selectedfrom a group of materials including Cu and TiN, for example.

The operations of FIGS. 1A through 1H may be repeated on the workpieceby a number of times until a desired thickness of ALD deposited film isreached. Prior to each repetition, an anneal process may be performed toremove the effects of the plasma treatment. Another way to remove theeffect of fluorocarbon plasma treatment is by exposing the surface toanother type of plasma such as, for example, an Ar plasma or a N plasma.

FIGS. 2A through 2H depict a process in accordance with a secondembodiment. In FIG. 2A, a workpiece surface 200 is patterned by aphotoresist layer 205 using photolithography, leaving portions of theworkpiece surface 200 exposed. In the next operation, a plasma treatmentoperation depicted in FIG. 2B, the workpiece surface 200 is exposed to afluoro-carbon plasma, forming a plasma treated surface layer 270 shownin FIG. 2C. The plasma treated surface layer 270 is formed in areasaligned with openings in the photoresist layer 205. Then, thephotoresist layer 205 is removed and replaced by a new photoresist layer210, as depicted in FIG. 2C. The pattern of the new photoresist layer210 may be slightly shifted relative to the previous photoresist layer205 (now removed), as shown in FIG. 2C. A second plasma treatment isperformed as depicted in FIG. 2D, forming an additional plasma treatedsurface layer 271 extending beyond the first plasma treated surfacelayer 270, as shown in FIG. 2E. The plasma treated surface layers 270and 271 are hydrophobic while the remainder of the workpiece surface 200is hydrophilic. The second photoresist layer 210 is removed and an ALDprocess is performed, as indicated in FIG. 2E. The resulting ALD growth240 shown in FIG. 2F occurs on the hydrophilic surfaces and has a narrowwidth W determined by the shift between the first and second photoresistlayers 205, 210.

FIG. 2G illustrates an example in which defects 250, such as unwantedALD growth nodules, are formed. The defects 250 are removed in an etchoperation, which decreases the thickness of the ALD growth 240, asdepicted in FIG. 2H.

The process of FIGS. 2A through 2H may be repeated a number of times toincrease the thickness of the ALD growth 240. Prior to each such repeat,an anneal operation may be performed to remove the effects of theprevious plasma treatments.

FIGS. 3A through 3H depict a process in accordance with a thirdembodiment. In FIG. 3A, a workpiece surface 300 is patterned by aphotoresist layer 305 using photolithography, leaving portions of theworkpiece surface 300 exposed. In the next operation, which is depictedin FIG. 3B, a first plasma treatment is performed by exposing theworkpiece surface 300 to a fluoro-carbon plasma. This produces a plasmatreated surface layer 370 indicated in FIG. 3C. Then, the photoresistlayer 305 is removed and a first ALD process is performed, as indicatedin FIG. 3C. The resulting ALD growth 340 shown in FIG. 3C coincides withlocations on the workpiece surface 300 not treated by the plasma andwhich are hydrophilic. Thereafter, the workpiece surface 300 issubjected to an anneal procedure (FIG. 3D) to remove the effects of theplasma treatment previously performed in FIG. 3B. This renders theexposed portions of the workpiece surface 300 hydrophilic. Next, asindicated in FIG. 3E, a second photoresist layer 310 is deposited on theworkpiece surface 300 as shown in FIG. 3E. The pattern of the newphotoresist layer 310 may be shifted relative to the previousphotoresist layer 305 (now removed), as shown in FIG. 3E. A secondplasma treatment is performed as depicted in FIG. 3F, which produces aplasma treated surface layer 371 extending beyond the plasma treatedsurface layer 370, as indicated in FIG. 3G. Then the second photoresistlayer 310 is removed and a second ALD process is performed, as indicatedin FIG. 3G. This second ALD process results in a second ALD growth layer341. The ALD growth layers 340 and 341 may be of the same or differentmaterials, depending upon the ALD processes employed. Next, theworkpiece surface 300 is subjected to an anneal procedure (FIG. 3H) toremove the effects of the fluoro-carbon plasma treatment of FIG. 3F.Another way to remove the effect of fluorocarbon plasma treatment is byexposing the surface to another type of plasma such as, for example, anAr plasma or a N plasma.

The foregoing process of FIGS. 3A through 3H may be repeated formulti-zone patterning of several or many different materials. Thematerials may include any material that can be formed by ALD, such as(but not limited to metals, non-metals, nitrides, metal oxides, HfO2,ZrO2, TiO2, SiO2, ZnO, and other similar materials, as some examples.

FIGS. 4A and 4B depict a process for ALD in selected areas, by employingshadowing effects of three-dimensional structures on the workpiecesurface. In FIG. 4A, a workpiece 400 has vertical surfaces 410 spacedapart by trenches 420, the vertical surfaces 410 comprising ahydrophilic material. Selected portions of the vertical surfaces 410 arechanged from hydrophilic to hydrophobic by treatment with a directionalplasma or plasma beam of a fluoro-carbon species. Also, the verticalsurfaces 410 are similarly treated. The plasma treatment forms plasmatreated surface layers 470.

The plasma beam includes two beams 461, 462, of respective beamdirections tilted through different angles, such as (for example) equaland opposite angles relative to the vertical surfaces 410. The tiltangle, the width of trench 420 and the depth of the trench 420 are suchthat the plasma beams 461, 462 do not reach bottom surface 460 of thetrench 420. The plasma-treated surface layers 470 extend partiallytoward the bottom surface 460.

Next, an ALD process is performed as depicted in FIG. 4B. The growth ofALD material 480 occurs inside the trench 420 starting at the bottomsurface 460 and progresses upwardly from the bottom surface 460. Theplasma-treatment changes the exposed surfaces from hydrophilic tohydrophobic, preventing ALD growth on the exposed surfaces.

FIGS. 5A and 5B depict a modification of the process of FIGS. 4A and 4B.In FIGS. 5A and 5B, only a single tilted plasma beam 560 is needed. InFIG. 5A, only one side (e.g., vertical surface 410 a) of each verticalfeature is exposed to plasma treatment to form a plasma-treated surfacelayer 471. The vertical surface 410 b is untreated and remainshydrophilic. As depicted in FIG. 5B, an ALD process is performed andproduces growth material 485 on the vertical surface 410 b.

In FIG. 6A, an untilted (vertical) plasma beam 660 is employed toperform plasma treatment. The result is that only horizontal surfaces(i.e., top surfaces 412 and bottom surfaces 460) are renderedhydrophobic by the formation of plasma treated surface layer 472. Next,an ALD process is performed as depicted in FIG. 6B, depositing an ALDgrowth material 490 on the vertical surfaces 410 only.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1-6. (canceled)
 7. A method of performing atomic layer deposition inselected zones of a workpiece, comprising: depositing a firstphotolithographic mask on said workpiece comprising first openingscorresponding to portions of said selected zones; treating saidworkpiece by exposure to species derived from a fluoro-carbon plasma;removing said first photolithographic mask; depositing a secondphotolithographic mask on said workpiece comprising second openingscorresponding to remaining portions of said selected zones; treatingsaid workpiece by exposure to species derived from a fluoro-carbonplasma; removing said second photolithographic mask; and performing anatomic layer deposition process.
 8. The method of claim 7 furthercomprising removing growth material from areas outside of said selectedzones.
 9. The method of claim 7 wherein said treating said workpiece byexposure to species derived from a fluoro-carbon plasma comprisesforming a fluoro-carbon plasma and exposing said workpiece to saidplasma.
 10. The method of claim 7 wherein said treating said workpieceby exposure to species derived from a fluoro-carbon plasma comprisesforming an ion beam from a fluoro-carbon plasma and directing said ionbeam to said workpiece.
 11. The method of claim 7 wherein said atomiclayer deposition process produces a growth material.
 12. A method ofperforming atomic layer deposition in selected zones of a workpiece,comprising: depositing a first photolithographic mask on said workpiececomprising first openings corresponding to portions of said selectedzones; treating said workpiece by exposure to species derived from afluoro-carbon plasma; removing said first photolithographic mask;performing a first atomic layer deposition process on said workpiece;depositing a second photolithographic mask on said workpiece comprisingsecond openings corresponding to remaining portions of said selectedzones; treating said workpiece by exposure to species derived from afluoro-carbon plasma; removing said second photolithographic mask; andperforming a second atomic layer deposition process.
 13. The method ofclaim 12 wherein said first and second atomic layer deposition processesdeposit different growth materials on said workpiece.
 14. The method ofclaim 12 wherein said treating said workpiece by exposure to speciesderived from a fluoro-carbon plasma comprises forming a fluoro-carbonplasma and exposing said workpiece to said plasma.
 15. The method ofclaim 12 wherein said treating said workpiece by exposure to speciesderived from a fluoro-carbon plasma comprises forming an ion beam from afluoro-carbon plasma and directing said ion beam to said workpiece. 16.The method of claim 12 wherein said first and second atomic layerdeposition process produce on said workpiece different respective growthmaterials.
 17. A method of performing atomic layer deposition inselected zones of a workpiece having 3-dimensional structures on asurface thereof comprising vertical walls separated by trenches,comprising: providing a directional plasma source emitting ions along anion propagation direction toward said workpiece; orienting said ionpropagation direction relative to said vertical walls to enable saidvertical walls to mask said selected zones from the ions emitted by saiddirectional plasma source; and performing an atomic layer depositionprocess on said workpiece.
 18. The method of claim 17 wherein saiddirectional plasma source emits ions in two beams tilted relative tosaid vertical walls through opposing angles and said two beams strikeopposing ones of said vertical walls.
 19. The method of claim 17 whereinsaid directional plasma source emits a beam tilted relative to saidvertical walls and said beams strikes one of said vertical walls. 20.The method of claim 17 wherein said directional plasma source emits ionsin one beam parallel to said vertical walls.